This disclosure relates generally to gas turbine engines and more particularly, to methods and systems to enhance flame-holding during turbine operation.
At least some gas turbine engines ignite a fuel-air mixture in a combustor to generate a combustion gas stream that is channeled downstream to a turbine via a hot gas path. Compressed air is channeled to the combustor from a compressor. Combustor assemblies typically have fuel nozzles that facilitate fuel and air delivery to a combustion zone defined in the combustor. The turbine converts the thermal energy of the combustion gas stream to mechanical energy that rotates a turbine shaft. The output of the turbine may be used to power a machine, for example, an electric generator or a pump.
At least some known fuel nozzles include a swirler assembly and a plurality of vanes that are coupled to the swirler assembly. During fabrication in some of such nozzles, a cover is coupled to the fuel nozzle assembly such that the cover substantially circumscribes the vanes. As such, an interior surface of the cover and an exterior surface of the swirler assembly define a flowpath for channeling flow through the fuel nozzle.
During operation, fuel is typically channeled through a plurality of passages formed within the swirler assembly and through a plurality of openings defined in at least one side of each vane. Known vanes may also include a cavity that is formed such that fuel channeled through the swirler assembly passages is discharged into the vane cavity. Moreover, each of such vanes includes a plurality of openings, commonly referred to as fuel injection holes, that extend through a sidewall of the vane and that are substantially normal to a surface of the vane sidewall to enable fuel channeled into the vane cavity to be channeled from the vane cavity through the sidewall injection hole to mix with the air stream that is flowing through the nozzle.
Moreover, in at least some known swirler assembly designs, vane flame holding may be different when using highly reactive fuels. Known methods to improve flame holding have included modifying a location, a number, and/or a size of the fuel injection holes. However, using known methods may decrease flame-holding margins of a fuel nozzle below desired allowable limits for high reactive fuels, such as syngas or high hydrogen fuel. Poor flame holding performance may create hot spots or streaks that exceed local maximum operating temperatures of the associated turbine engine and/or damage the fuel nozzle. Although such known methods have provided some improvements in fuel nozzle performance, there still exists a desire to improve fuel nozzle performance and to enhance flame holding characteristics.